Portable consumer electronic products such as mobile phones, tablet computers and handheld game consoles are becoming more and more popular with consumers. These electronic products normally use vibration signal as feedback information, for example, mobile phones have incoming call reminder, and handheld game consoles have vibration feedback. The vibration feedback function has become the most important application of vibration motors in the field of consumer electronics.
The structure of a linear vibration motor in prior art is as follows: a suspension component is made of a magnet and a high specific gravity alloy mass block, a coil is fastened on a bottom plate of a housing, the suspension component is provided inside the housing and is driven by electromagnetic force to move back and forth in a direction parallel to the bottom plate of the housing. This type of structure is generally called a “moving-magnet” structure, but it has a major disadvantage: when the magnetic induction line of the magnet directly faces the coil and is perpendicular to the coil, the generated electromagnetic force is parallel to the bottom plate, and thus the coil is driven by electromagnetic force to move parallel to the bottom plate; however, because the magnetic induction line generated by the magnet is arc-shaped, when the magnet moves to either of the two lateral sides, the magnetic induction line is not perpendicular to the coil, and thus the generated electromagnetic force has a horizontal force component parallel to the bottom plate of the housing as well as a vertical force component perpendicular to the bottom plate of the housing, wherein the vertical force component causes the magnet to move in a vertical direction of the housing. The vertical direction refers to the thickness direction of the housing, along which the thin-type linear motor has a smallest dimension with very narrow space, and as a result, the suspension component collides with the housing in its vertical motion and causes noise.
Meanwhile, during use of a linear motor, a metal plate made of high magnetic conductivity material such as ferrum, cobalt, nickel is provided adjacent to an outer side of the housing, and since the suspension vibrator contains magnet, under the influence of attraction force of this magnetic metal plate, the vibrator tends to deviate from its normal balance position. In a situation of severe attraction force, the vibrator would be “stuck to” the housing surface, causing vibration failure of the motor that loses vibration function. In order to solve this problem, in prior art, a shield plate with high magnetic conductivity is fixed onto the housing surface on each of the two sides of the suspension component so as to shield any influence of external magnetic field towards the suspension component inside the motor and minimize the deviation degree of the suspension component towards the housing. However, the shield plate itself has high magnetic conductivity and tends to attract the magnet within the suspension component. The two shield plates on both sides of the suspension component simultaneously attract the suspension component, and it is very difficult for the magnet mounted on the mass block to be arranged such that the attraction forces of the two shield plates towards the vibrator's magnet are exactly equal, therefore, in a situation of uneven force, the suspension component would move in the thickness direction of the housing and thus collide with the housing.